DESCRIPTION: The goal of this application is testing the novel hypothesis that the periodontal pathogen Porphyromonas gingivalis (P.g.) interferes with the interactions between oral keratinocytes (OK) and extracellular matrix (ECM), and may cause loss of epithelial integrity. P.g. is a well-known oral pathogen with several distinct virulence factors, which may contribute to P.g. pathogenicity. We intend to focus on those factors that directly or indirectly affect OK/ECM interactions. Our preliminary data show that P.g. alters OK cell morphology, adhesion, migration and survival, and induces proteolysis of OK proteins. Our project is articulated into3 Aims, with the purpose of investigating the molecular mechanisms, both cellular and bacterial, which may underlie these P.g. effects on ECM related functions in OK. In Aim 1, we will analyze the specificity of P.g. interference towards ECM macromolecules that are characteristically found either in normal (e.g. laminin-5 and collagen) or in chronically diseased (e.g. fibronectin and vitronectin) periodontal tissue. To this end, adhesion, migration and survival assays on specific ECMs will be performed with continuous OK cell lines in the presence of P.g. Furthermore, we will compare cellular effects of P.g. with those possibly induced by other oral bacteria, both pathogenic and not. In Aim 2, we will determine whether P.g. alters ECM related functions in OK by interfering with integrin expression and activation state, cytoskeletal organization, and/or modification of integrin-proximal and distal transduction pathways, focusing on the effect of P.g. gingipains. In Aim 3, we will test specific P.g. and other bacterial factors such as proteinases and fimbriae for their possible effects on OK/ECM interactions, by comparing P.g. wild-type versus well-defined virulence mutant strains, using as a guide data from Aim 1 and 2. Results from these approaches will hopefully provide new and exciting molecular clues as to the mechanisms whereby P.g. may initiate and sustain periodontal disease. Such clues may be useful for devising new modalities of treatment and prevention.